To a 0 ̊C solution of macrocycle 6 (1.55g, 3.29 mmol) in MeOH (50 mL) was added dropwise another solution of PIDA (1.02g, 3.29mmol) in MeOH (15.8 mL) over 10 min. After stirring for 5 min, the reaction mixture was concentrated to 1/5th volume via rotoevaporation. The concentrated reaction mixture was diluted with saturated aqueous NaHCO3 (20 mL) and water (10 mL). The resulting mixture was extracted with DCM(25 mLx 5). The combined organic phases were dried over Na2SO4 and concentrated under vacuum to give crude α-methoxy enone10asa yellow foam (2.2 g), which was used for the next reaction without further purification.
